Question 116148
Since order does matter, we must use the <a href=http://www.mathwords.com/p/permutation_formula.htm>permutation formula</a>:





*[Tex \LARGE \textrm{_{n}P_{r}=]{{{n!/(n-r)!}}} Start with the given formula




*[Tex \LARGE \textrm{_{5}P_{0}=]{{{5!/(5-0)!}}} Plug in {{{n=5}}} and {{{r=0}}}




*[Tex \LARGE \textrm{_{5}P_{0}=]{{{5!/5!}}} Subtract {{{5-0}}} to get 5




Expand 5!
*[Tex \LARGE \textrm{_{5}P_{0}=]{{{(5*4*3*2*1)/5!}}}




Expand 5!
*[Tex \LARGE \textrm{_{5}P_{0}=]{{{(5*4*3*2*1)/(5*4*3*2*1)}}}




*[Tex \LARGE \textrm{_{5}P_{0}=]{{{(cross(5*4*3*2*1))/(cross(5*4*3*2*1))}}}  Cancel like terms




*[Tex \LARGE \textrm{_{5}P_{0}=]{{{1}}}  Simplify





So 5 choose 0 (where order does matter) yields 1 unique combination